Bently Nevada 3500/45 4-Channel Position Monitor

Bently Nevada 3500/45 position monitor for thrust, expansion and valve position

The Bently Nevada 3500/45 Position Monitor is a four-channel monitor for the 3500 machinery protection rack that measures how far a machine part has moved rather than how fast it vibrates. It accepts proximity probe systems, rotary position transducers, DC and AC LVDTs and rotary potentiometers, conditions the signal, and compares it with user-programmable Alert and Danger alarms. The part number 3500/45 refers to the monitor itself; the manufacturer lists the spare main module as 176449-04, and the matching rear I/O module is chosen by the code that follows the model number.

Typical jobs are axial (thrust) position on a rotor, differential expansion between rotor and casing, case expansion and valve position. Seven Star LLC supplies the 3500/45 in Oman and the GCC as an independent supplier in Muscat.

3500/45 technical specifications

Decoding 3500/45-AA-BB

External-termination I/O modules need the termination blocks and cables ordered separately. The blocks are 125808-06 (Euro style, Proximitor/RPT/DC LVDT), 128015-06 (terminal strip), 141208-01 (Euro style, AC LVDT), and the recorder blocks 128702-01 and 128710-01. Cable families are 129525-AAAA-BB for transducers and 129529-AAAA-BB for recorder outputs.

How the 3500/45 measures position

For thrust, a proximity probe looks at the thrust collar or shaft end, and the gap voltage from the Proximitor moves as the rotor shifts. The monitor treats that DC gap as the position and flags motion toward or away from the active thrust bearing. For differential expansion the monitor combines rotor-to-case probes, using single or dual ramp methods for large expansion ranges, and in complementary input mode uses two probes whose signals complement each other. LVDTs convert linear displacement into a voltage, which is how case expansion and valve position are measured.

Each channel typically produces several measured variables such as direct, gap and composite values. Alert setpoints can be set on each active measured variable and Danger setpoints on any two.

Where the 3500/45 fits in the rack

Any of the 14 slots to the right of the TDI can hold a position monitor. The 3500/45 shares the rack with proximitor monitors such as the 3500/40M and 3500/42M, relay modules like the 3500/33, the 3500/25 Keyphasor module and the communication gateways. Firmware and software minimums quoted by the manufacturer for adding it to an older system are 3500/20 RIM firmware revision G, 3500 Configuration Software 2.41, Data Acquisition 2.20 and Operator Display 1.20. Valve position using an RPT needs Configuration Software 3.00 or later.

Selection checklist for the 3500/45

• Define the measurement per channel pair: thrust, differential expansion (and which ramp type), case expansion or valve position.
• Identify the transducer. Proximitors and RPT use the 01/02 I/O type, while AC LVDTs need the 05/06 I/O type.
• Choose between internal and external terminations to match the cabinet wiring.
• Match the agency approval to the area classification, and check the supplied label.
• For differential expansion on ramp configurations, review the accuracy table in the datasheet, which ranges from ±1.0% to ±2.0% of full scale depending on ramp angle, span and transducer match.

Installation, commissioning and maintenance

Set probe gaps and verify scale factors with a micrometer-type calibrator before locking in the alarm setpoints. On thrust channels, set the zero position with the rotor held at its thrust bearing position, as defined in the machine manual, and confirm the direction of the position change against the rotor movement. For LVDTs, check the null and span through the full stroke.

When replacing a module, verify that the stored rack configuration matches the new I/O, check that the OK and TX/RX LEDs are healthy, and bypass the channels using the rack bypass function during testing so that no unintended trip is issued. Keep spares of the monitor and of each I/O type used on your fleet.

Typical applications in Oman and the GCC

Thrust position protection is standard on steam turbines, gas turbines, large centrifugal compressors and pumps in the oil and gas, power and petrochemical plants of Oman and the GCC. Differential and case expansion monitoring matter at start-up of steam turbines in power and desalination stations, where thermal growth must be controlled. Valve position monitoring supports steam and fuel control valves. Wide daily and seasonal temperature swings in the region make accurate gap and thermal-growth data important during commissioning.

Information to send with your RFQ for the 3500/45

• Complete ordering code (for example 3500/45-01-00) or the part number 3500/45, plus quantity.
• Label photos of the monitor and I/O module, with revision.
• Transducer types and measurement functions per channel.
• Rack details, delivery country and required date.

Related Bently Nevada products: Bently Nevada 3500/72M Recip Rod Position Monitor, Bently Nevada 3500/46M Hydro Monitor, Bently Nevada 3500/32M 4-Channel Relay Module, Bently Nevada 3500/42M Proximitor Seismic Monitor, Bently Nevada 3500/44M Aeroderivative GT Vibration Monitor and Bently Nevada 3500/64M Dynamic Pressure Monitor.

Documents and quotation

The 3500/45 Position Monitor datasheet is attached on this page and is the reference for the figures above.

Send the 3500/45 code you need and the rack details, and Seven Star LLC will confirm availability and lead time in the quotation for Oman and the GCC.